This is an optional Exotek Mini 8IGHT-T Shorty LiPo Block Set. When combined with the Exotek Mini 8IGHT-T chassis (EXO1471), these aluminum LiPo blocks allow the use of higher capacity/higher power 1/10 Shorty packs! This heavy duty mounting system is more secure, and is compatible with the stock battery strap, as well as the Exotek carbon strap (EXO1240).